Glioblastoma is the most common and most aggressive type of malignant brain tumor. The drug pazopanib is used to treat people with a type of kidney cancer. Topotecan is used to treat lung cancer. Both topotecan and pazopanib have individually been used to treat patients with glioblastoma and some anti-tumor activity has been found. Researchers want to see if these two drugs together may be able to help people with glioblastoma.